Abstract: A light emitting diode (LED) backlight driving circuit includes an LED lightbar, and a constant current chip that controls current flowing through the LED lightbar. The LED backlight driving circuit further includes a comparison module that receives an output voltage of the LED lightbar. When the output voltage of the LED lightbar is greater than the preset reference voltage, the comparison module controls the constant current chip to switch off the current of the LED lightbar.

Abstract: A LED driving device adapted to driving N LED strings connected in series is provided. N is a positive integer greater than 1. The LED driving device includes (N?1) switch units, a current source, a detection unit and a control unit. The ith switch unit electrically connects to the (i+1) LED string in parallel or to the ith LED string in parallel, and 0<i?(N?1). The current source supplies a driving current to drive the N LED strings. The detection unit outputs a detection signal according to a voltage of the current source, a first reference voltage and a second reference voltage. The control unit outputs a plurality of first control signals according to the detection signal to dynamically control an amount of the (N?1) switch units turned on.

Abstract: A method for controlling a portable lighting device. The device has a switched-mode power supply, a light source, a high frequency switch, a controller controlling the operation of the light source and a user interface for inputting commands to the controller. A DC power source has a negative pole that is connected by only one single electric contact with the lighting device tail. The method for controlling a portable lighting device includes connecting a DC power source, an inductor, a light source, a high frequency switch and a resistor in series, measuring a voltage across the resistor, and controlling the high frequency switch dependent on the voltage measured across the resistor.

Abstract: The present invention provides an illumination device, an illumination system, and a lamp. The illumination system includes the illumination device and a light modulation module. The illumination device includes a light emitting diode (LED) array, an alternating current (AC) current source, and an output power control module. The AC current source is electrically coupled to the LED array. The output power control module is electrically coupled to the LED array and the AC current source. The LED array, the AC current source, and the output power control module together form a closed-loop control loop. The light modulation module is electrically coupled to the closed-loop control loop for modulating illumination brightness of the LED.

Abstract: A lighting power source according to an embodiment includes a rectification circuit, a smoothing capacitor, a waveform shaping circuit, and a DC-DC converter. The rectification circuit rectifies an AC voltage input thereto. The waveform shaping circuit is connected between the rectification circuit and the smoothing capacitor, performs a switching operation to repeat an ON state and an OFF state when the voltage output from the rectification circuit is relatively high, continues to be in the ON state to allow the current to flow to the rectification circuit when the voltage output from the rectification circuit is relatively low. The DC-DC converter converts a voltage charged in the smoothing capacitor.

Abstract: An electronic ballast for driving a light-emitting device, includes a square wave generator having a plurality of switch elements for converting a DC input voltage into a square-wave AC voltage. A transformer has a driving winding and a plurality of inductive windings mutually connected with each other, in which at least a portion of the inductive windings are respectively connected to a control terminal of the switch element. A resonant circuit connects the driving winding and a light-emitting device and converts the square-wave voltage into an AC output voltage to drive the light-emitting device. An auxiliary control unit connected to the transformer regulates a voltage waveform of the driving winding or a voltage waveform of the inductive winding according to a control signal, thereby changing the voltage waveform of the inductive winding connected to the switch element to adjust the switching frequencies of the switch elements.

Abstract: An illustrative LED driver circuit includes dimming control of the LED lamp. The circuit uses flyback converter topology, a power factor correction (PFC) primary side controller, a secondary side controller that includes current control and voltage control regulation, and an dimming control circuit. The dimming control circuit includes a selectable dimming control signal added together with a sensed current output signal to provide a control signal supplied to the secondary controller for output current control.

Abstract: An LED drive device includes: a drive module generating, based on a control signal, a drive current that flows through an LED-based load, and generating, based on the drive current, a sampling current associated with the drive current; a voltage detection module detecting a voltage across the LED-based load, and generating an adjustment signal based on the detection result and on a predetermined reference voltage; and a control signal generation module generating the control signal based on the adjustment signal, the sampling current and the predetermined reference voltage.

Abstract: Aspects of the disclosure provide a method for driving dimmable load. The method includes detecting a dimming characteristic in an energy source from which a load draws a first energy according to the dimming characteristic. The dimming characteristic requires a second energy in addition to the first energy to be drawn from the energy source to sustain an operation of the energy source. The method further includes biasing a switch to consume the second energy. The second energy and the first energy are drawn from the energy source to sustain the operation of the energy source.

Abstract: A protection circuit of a DC-DC converter is disclosed. An input terminal of the DC-DC converter receives an input voltage and an output terminal of the DC-DC converter provides an output voltage. The DC-DC converter includes an output stage between the input terminal and the output terminal. The protection circuit includes a current sensor, a comparator, a determining circuit, and a protection control circuit. The current sensor provides a sensing signal. The comparator compares a default over-voltage with the sensing signal to provide an over-current control signal. The determining circuit provides a determining control signal. The protection control circuit determines whether to enable a short protection according to the over-current control signal and the determining control signal.

Abstract: An LED lamp control circuit comprises a rectifier circuit, an LED light source load, a constant current circuit, and a first temperature detect switch circuit. The LED light source load comprises at least one group of LEDs. The constant current circuit comprises at least one group of constant current source components, each of which is connected to at least one group of LEDs in the LED light source load and comprises a depletion mode field effect transistor. The first temperature detect switch circuit is connected to an input end of a power source, and comprises a first normally closed temperature detect switch mounted on a radiator. When the temperature of the radiator exceeds the disconnection temperature of the first normally closed temperature detect switch, the first normally closed temperature detect switch is disconnected, so as to cut off the power supply of the LED light source load.

Abstract: The lighting apparatus in accordance with the present invention includes: a switching regulator including a switching element; and a control circuit configured to adjust a switching frequency and on-duration of the switching element in accordance with a dimming ratio. The control circuit is configured to, when the dimming ratio falls within a first dimming range, adjust the switching frequency to a frequency associated with the first dimming range and adjust the on-duration to duration corresponding to the dimming ratio. The control circuit is configured to, when the dimming ratio falls within a second dimming range, adjust the on-duration to duration associated with the second dimming range and adjust the switching frequency to a frequency corresponding to the dimming ratio.

Abstract: A lighting device for a solid-state light source includes a DC power source circuit section which flows a current in a solid-state light source by using a charging/discharging current or either one of charging and discharging currents of a inductor connected in series to a switching element, and a current control section having a first switching control unit for changing an ON width of the switching element depending on a dimming level and a second switching control unit for controlling an ON timing of the switching element. The second switching control unit changes a time until the switching element is turned on from a zero-crossing of the discharging current of the inductor such that the time becomes substantially the same when the dimming level is equal to or greater than a predetermined level, and the time becomes longer when the dimming level is less than the predetermined level.

Abstract: A self-oscillating resonator (SOR) may be used to control current through light emitting diodes (LEDs). The SOR may be started and stopped by a controller coupled to a transistor switch in the SOR. The controller may output a control signal that starts and stops the SOR by coupling a supply voltage or a ground to a base of the transistor switch in the SOR. Additional control over the current output to the LEDs may be gained through a resistive DAC coupled to the SOR and duty cycling the SOR.

Abstract: A universal load control module may include a power supply that operates over a wide voltage range, a microcontroller, and one or more functional control blocks. A functional control block may include a dimmer circuit for controlling a lighting load that provides reverse phase cut mode dimming, forward phase cut mode dimming, and hybrid phase cut mode dimming, as well as thermal protection. One or more universal control modules may be housed in a cabinet that include a cabinet control module. The cabinet may include additional thermal protection measures.

Abstract: A lighting device having an electrical circuit includes an LED having a variable illuminating resistance. The electrical circuit is configured for energizing the LED light source with a source of electrical power. The LED light source is energized with an effective power such that the LED light source functions in accordance with a targeted illuminating resistance. The circuit includes one or more components for monitoring circuit parameters, calculating the illuminating resistance of the LED and for changing the effective power applied to the LED light source in response to a relationship between the illuminating resistance and the targeted illuminating resistance. The change in effective power made by the circuit is for returning the illuminating resistance to a predetermined relationship with the targeted illuminating resistance.

Abstract: Methods and apparatus for controlling a high intensity discharge lamp and a power supply system for the high intensity discharge lamp are disclosed. The system relates to a method for controlling high intensity discharge lamp comprising supplying a signal of variable frequency and constant filling factor from a switches cascade to a ballast circuit and the lamp, said ballast circuit having at least one condenser and at least one inductance. The method uses the signal of periodically fluctuating frequency and constant filling factor of 50%, supplied from the electronic switches cascade of the half-bridge type, connected with the ballast circuit and the lamp, where the ballast circuit includes at least first condenser, the lamp and includes first inductance and second condenser forming a resonant circuit. A supply system for high intensity discharge lamp is also disclosed.

Abstract: A lighting device has a direct-current power generation circuit, a rectangular-wave generation circuit, a pulse generating circuit, lamp-voltage detection means, and pulse-generation command means. The direct-current power generation circuit generates direct-current power from external power. The rectangular-wave generation circuit converts the direct-current power to rectangular-wave alternating-current power. The pulse generating circuit superposes high-voltage pulses on the rectangular-wave power output from the rectangular-wave generation circuit and starts a discharge lamp. The lamp-voltage detection means detects, in digital form, a lamp voltage supplied to the discharge lamp. The pulse-generation command means issues a pulse generation command to the pulse generating circuit when the value detected by the lamp-voltage detection means reaches a predetermined no-load-voltage determination level.

Abstract: A plasma supply device generates an output power greater than 500 W at an essentially constant basic frequency greater than 3 MHz and powers a plasma process to which is supplied the generated output power, and from which reflected power is returned to the plasma supply device. The plasma supply device includes at least one inverter connected to a DC power supply, which inverter has at least one switching element, and an output network, wherein the at least one output network includes at least one inductance that has at least one magnetic field strengthening element that is a Perminvar ferrite.

Abstract: A discharge lamp system includes a discharge lamp, a power source, a converter, a lamp state signal detection module and a controller. The power source provides a DC power. The converter converts the DC power into a current required by the discharge lamp. The lamp state signal detection module receives a lamp state signal and outputs a lamp state detection signal. The controller processes the lamp state detection signal and a given synchronization signal to generate an average lamp current signal and a pulse current signal, and then processes the average lamp current signal and the pulse current signal to generate a control signal. The controller performs current control of the discharge lamp through the converter according to the control signal. Furthermore, a method for controlling a discharge lamp is also disclosed herein.

Abstract: A drive circuit for realizing accurate constant current of multiple LEDs is disclosed. The drive circuit comprises a high-frequency impulse Alternating Current (AC) power carrying N circuit units with same structure. Each of the circuit unit comprises a rectifier filter circuit, a blocking capacitor C1 and two LED loads. The rectifier filter circuit comprises two independent half-wave rectifier circuits, and two filter capacitors. Each of the two half-wave rectifier circuits comprises two diodes connected in series to supply power for the corresponding LED load. The filter capacitor is connected in parallel with the two ends of an LED load respectively, and the blocking capacitor C1 is connected in series with the input end of the rectifier filter circuit. The circuit also comprises N?1 equalizing transformers, each of which connects in series between two adjacent circuit units.

Abstract: The present invention relates to a high efficiency LED driver and driving method thereof. In one embodiment, a high efficiency LED driving method configured for a LED device can include: (i) receiving a DC bus voltage and generating a driving voltage for the LED device through a power switch; (ii) comparing the DC bus voltage against a sum of the driving voltage and a first reference voltage; (iii) where when the DC bus voltage is greater than the sum of the driving voltage and the first reference voltage, generating a first output current; (iv) where when the DC bus voltage is greater than the driving voltage and less than the sum of the driving voltage and the first reference voltage, generating a second output current; and (v) matching an average current of the first output current and the second output current with a corresponding driving current.

Abstract: A lighting device includes: a series circuit of an inductor and a switching element; a diode which regenerates and supplies an energy of the inductor; and a control circuit which controls on/off of the switching element. The control circuit includes a drive signal generator which outputs a high frequency pulse drive signal; and a drive control section which turns on and off the switching element based on the high frequency drive signal and a PWM signal. The drive signal generator changes an ON time of the high frequency drive signal such that, after the PWM signal is changed from OFF to ON, a peak value of the load current gradually drops along an envelope of a specific slope, and the specific slope of the envelope is changed based on a duty ratio of the PWM signal.

Abstract: The present invention discloses a light emitting device power supply circuit and a damping circuit therein and a driving method thereof. The light emitting device power supply circuit includes: a tri-electrode AC switch (TRIAC) dimming circuit, a rectifier circuit, a light emitting device driver circuit, and a damping circuit. The damping circuit includes: an impedance circuit, which is electrically connected between the rectifier circuit and the light emitting device driver circuit; a silicon control rectifier (SCR) circuit, which is connected to the impedance circuit in parallel; and a delay circuit, which is coupled to the SCR circuit, for turning ON the SCR circuit after a delay time period from when the TRIAC diming circuit begins to start-up, wherein the delay circuit does not directly receive a full scale of the input voltage.

Abstract: A power supply for illumination includes a detection circuit and a control circuit. The detection circuit compares an AC voltage whose phase is controlled with a first threshold voltage so as to detect a variation in a conduction state of phase control in the AC voltage, and compares the AC voltage with a second threshold voltage lower than the first threshold voltage so as to detect a zero-cross point of the AC voltage, thereby detecting a conduction period of the phase control. The control circuit outputs an output current according to the duration of the conduction period.

Abstract: A lamp driver responsive to a control signal that is variable in a predetermined control range includes a circuit operable in response to a value of the control signal within the predetermined control range to develop a first current and a lamp control voltage dependent upon the value of the control signal. A shutdown interface is operable in response to a value of the control signal outside of the predetermined control range to develop a second current to turn off a lamp.

Abstract: A circuit configuration for powering electrical loads, especially light emitting diodes, using a DC voltage converter with controllable switching element.

Abstract: Driver arrangements (100) drive first organic light emitting diode circuits (1) coupled to reference terminals (10) and first output terminals (11) and drive second organic light emitting diode circuits (2) coupled to the first output terminals (11) and to second output terminals (12). The driver arrangements (100) comprise first/second elements (21/22) coupled to the first/second output terminals (11) and the reference terminals (10) and first/second switches (31/32) coupled to power source terminals (14) and the first/second output terminals (11/12) for controlling the stacked organic light emitting diode circuits (1, 2) individually. The switches (31, 32) and the first elements (21) comprise transistors and the second elements (22) comprise transistors or diodes. The first/second elements (21/22) and the first/second switches (31/32) are coupled to each other and via first/second inductors (41/42) to the first/second output terminals (11/12).

Abstract: A dimmable light emitting lamp configured to interface with cat-ear dimmer switches. The lamp includes one or more light emitting devices. The lamp also includes circuitry configured to receive an input voltage and provide regulated current to the one or more light emitting devices. The input voltage has a first voltage pulse that does not represent a dimming level of a dimmer switch and a second voltage pulse that represents the dimming level of the dimmer switch. The circuitry determines a first duration corresponding to a length of the first voltage pulse and a second duration corresponding to a length of the second voltage pulse responsive to first duration. The circuitry adjusts the regulated current to the light emitting devices according to the second duration to adjust output light intensity of the light emitting devices.

Abstract: The present invention discloses a dimming control circuit and a method for generating analog and digital signals according to an analog control signal. The dimming control circuit according to the present invention comprises an input for receiving an analog control signal; a digital dimming circuit for receiving the analog control signal and generating a digital signal; an analog dimming circuit for receiving the analog control signal and generating an analog signal; and a power circuit enabled by the digital signal for converting a supply voltage to an output voltage according to the analog signal generated by the analog dimming circuit.

Abstract: This disclosure relates to illumination systems. In particular it relates to a method and system for avoiding flicker (in particular 100 Hz or 120 Hz flicker) in solid state lighting devices such as LED or OLED assemblies. A controller for a driver circuit of a solid state lighting device (SSL) is described. The driver circuit comprises a power converter to convert a varying input voltage into a drive voltage for the SSL device. The input voltage is derived from a rectified AC mains voltage and frequency. The power converter is used with a maximum voltage step-up conversion ratio. The controller synchronizes to the mains frequency and determines a plurality of pulse intervals repeated at a pulse frequency where the pulse frequency is greater than a perceptual frequency of light intensity variations perceivable by a human eye.

Abstract: A driver circuit for driving an LED includes a rectifier circuit to receive AC voltage and to convert the AC voltage to DC voltage. The driver circuit further includes a filter circuit for filtering the DC voltage. The driver circuit further includes a detection circuit for determining a change in the filtered DC voltage over a predetermined time interval. The driver circuit further includes a dampening circuit for dampening the filtered DC voltage responsive to the detection circuit determining that the change in filtered DC voltage over the predetermined time interval exceeds a predetermined threshold.

Abstract: An improved LED module that is thermally self-stabilizing, and that is able to be retrofitted into an existing flashlight is provided. In one embodiment, the LED module includes a light emitting diode, an amplifying circuit and a microchip. The amplifying circuit includes a temperature sensing device to sense heat from the light emitting diode. The output of the amplifying circuit is input to the microchip which output to a switching device that regulates energy that is delivered to the light emitting diode. The switching device may be part of a boosting circuit, a bucking circuit or an inverting circuit.

Abstract: A system includes a transformer. The transformer includes a first coil and a second coil. The first coil is configured to receive a first voltage based on an output of a switching circuit. The second coil is configured to generate a first current based on the first voltage to power a solid-state load. The system also includes a third coil. The third coil is configured to generate a second voltage based on the first voltage.

Abstract: The invention discloses an illumination control circuit and an illumination control method. The illumination control method includes modulating an alternating current input signal and accordingly generating a dimming signal, which includes several waveform pulses each with an adjustable conduction angles; continuously sampling the waveform pulses of the dimming signal and forming an average waveform pulse from the sampled waveform pulses; extracting the average waveform pulse, which has an average conduction angle corresponding to the conduction angles of the waveform pulses; performing an integration on the sampled average waveform pulse and accordingly generating a current-controlling signal; and driving an illumination lamp according to the current-controlling signal.

Abstract: An LED AC driving circuit capable of adjusting operating voltage has a rectifying unit, an LED unit, a voltage-controlled transistor, a current detecting unit and a current regulating unit to form a power loop. Further, a resistance adjusting unit is connected to the voltage-controlled transistor in parallel. The current regulating unit detects the operating power of the voltage-controlled transistor. When the detected operating power is zero, the resistance of the resistance adjusting unit is increased for increasing the current flowing through the voltage-controlled transistor. When the detected operating power becomes larger than a maximum rated power, the resistance of the resistance adjusting unit is decreased to reduce the current. Thus, the operating power is maintained between zero and the maximum rated power.

Abstract: A lighting apparatus includes an input power terminal, a light source element coupled to the input power terminal, and a current bleeder module that is connected to the input power terminal and is configured to draw a current from the input power terminal responsive to a phase cut input power signal received at the input power terminal during a first portion of a period of the phase cut input power signal and is configured as an open circuit so as not to draw current from the input power terminal during a second portion of the period of the phase cut input power signal.

Abstract: A circuit for powering a LED light source includes a converter and a controller. The converter provides an output voltage, and includes a first switch which is turned on and off alternately according to a driving signal to control a current. The controller generates the driving signal which is a periodic signal having a first state and a second state per time period. The first switch is turned on when the driving signal operates in the first state, and is turned off when the driving signal operates in the second state. The controller modulates a time period of the driving signal and a time duration of the first state, such that a quotient of the time duration squared and the time period is substantially independent of a change of the time period, and the current is substantially independent of the change.

Abstract: Various embodiments of a dimmable power supply are disclosed herein. For example, some embodiments provide a dimmable power supply including an input current path, a switch in the input current path, an energy storage device connected to the input current path, a load output connected to the energy storage device, and a timer-based variable pulse generator connected to a control input of the switch. The timer-based variable pulse generator is adapted to generate a stream of pulses having a variable on-time and off-time. The dimmable power supply is adapted to vary the on-time and off-time to control a current at the load output.

Abstract: A circuit includes a converter and a controller. The converter includes a switch which is turned on and off alternately according to a driving signal to control a current. The controller generates the driving signal which is a periodic signal having a first state in a first time duration and having a second state in a second time duration and in a third time duration per period of the driving signal. The controller modulates the first time duration and the second time duration to have a change rate, and modulates the third time duration equal to a product of the change rate and a sum of the first time duration and the second time duration, such that a quotient of the first time duration squared and the period of the driving signal is independent of a change of the first time duration, and the current is independent of the change.

Abstract: The present invention relates to an apparatus for automatically controlling illuminance, which transmits a dimming signal based on the zero-crossing of AC power using an illuminance control electronic switch. An apparatus for automatically controlling illuminance of Light-Emitting Diode (LED) lighting according to an embodiment of the present invention includes a dimming control electronic switch for, if manipulation of a switch by a user is sensed during supply of Alternating Current (AC) power to an LED lamp, interrupting supply of the AC power during a preset period of time based on zero-crossing of the AC power, and an LED lamp control device for controlling illuminance of the LED lamp by detecting supply and interruption of the AC power.

Abstract: A dimmable LED driver circuit comprises a resonant DC-DC converter coupled to an output circuit. The converter comprises a half bridge or full bridge switching circuit coupled to a resonant circuit. An output of the resonant circuit is rectified and fed to the output circuit. The output circuit may comprise at least one LED series or shunt switch for switching an LED unit on and off. A control circuit controls the switches of the switching circuit at a variable switching frequency. The control circuit is also configured for controlling the switching circuit for amplitude modulating the converter and for pulse-width modulating the converter at a first pulse-width modulation frequency lower than the switching frequency. The control circuit is may further be configured for controlling the switching of the LED switch at a second pulse-width modulation frequency lower than the switching frequency.

Abstract: A two wheeled vehicle includes a main body, a first wheel that is coupled to the main body, and a second wheel that is coupled to the main body. The vehicle also includes a motor that is supported by the main body and that drives at least one of the first and second wheels in rotation relative to the main body. Moreover, the vehicle includes a controller assembly including a controller and a controller housing. The controller is operable to control the motor to thereby control driving rotation of the at least one of the first and second wheels. The controller is housed within the controller housing, and the controller housing is coupled to the main body. The controller and the motor are in severable but operable communication when the controller housing is coupled to the main body.

Abstract: A detect method is provided for performing step dimming selection in an electronic ballast including an End of Lamp Life detect circuit and a half-bridge inverter, the End of Lamp Life detect circuit being connected to an input terminal of the control circuit, wherein each time when the power switch is turned on, it is judged whether the electronic ballast should enter the dimming mode or not by detecting the voltage at the input terminal of the control circuit before the half-bridge inverter starts operating.

Abstract: This invention relates to a power factor correction circuit of an electronic ballast. The electronic ballast includes a rectification circuit, a first capacitive element and an inverter. The power factor correction circuit comprises a unidirectional element, an inductive element and a second capacitive element. The unidirectional element is connected in series with the inductive element, and the second capacitive element is connected in parallel with the unidirectional element and the inductive element. A junction of the unidirectional element and the second capacitive element is coupled to a first output terminal of the rectification circuit, a junction of the inductive element and the second capacitive element is coupled to an input terminal of the inverter, and the first capacitive element is coupled between a second output terminal of the rectification circuit and a junction of the unidirectional element and the inductive element.

Abstract: An LED driver circuit includes: a bridge rectifier, a first compensation capacitor, a second compensation capacitor, and an LED module. The bridge rectifier is connected to an AC input power for producing a rectification output power. The first compensation capacitor is connected to a first rectification output terminal and an AC input terminal of the bridge rectifier. The second compensation capacitor is connected to a second rectification terminal and the AC input terminal of the bridge rectifier. The LED module is connected to the first rectification output terminal and the second rectification output terminal of the bridge rectifier. The first and second compensation capacitors in the present invention can effectively improve the total current harmonic distortion of the LED module and its utilization.

Abstract: A lighting device has a power-factor correction circuit 6, a step-down chopper circuit 8, a full-bridge circuit 10, control ICs for these circuits and a driving-voltage supply circuit 14. The supply circuit 14 supplies a driving voltage to the control ICs. The control IC outputs the on/off driving voltage to a switching element of the corresponding circuit 6 to 10. The lighting device also has a detector 16 and judgment equipment 18. The detector 16 detects the driving voltage supplied from the supply circuit 14. The judgment equipment 18 instructs the control ICs to start outputting the on/off driving voltages in the order from the control IC close to the power source 2 to the control IC close to the discharge lamp 4 when the driving voltage detected by the detector 16 reaches a predetermined value during the time when the driving voltage supplied from the supply circuit 14 rises.

Abstract: A light source driving apparatus including a voltage converting unit, a switching unit, a feedback unit and a control unit is provided. The voltage converting unit provides a driving current to drive a light source module. The switching unit is controlled to be conducted or not by a switch signal. The feedback unit detects a load status of the light source module, and provides a feedback signal accordingly. The control unit modulates pulse widths of the switch signal according to the feedback signal, a signal upper limitation, and a signal lower limitation, so as to control the switching unit to be conducted. The voltage converting unit includes an energy storage element. When the switching unit is conducted, the energy storage element stores a part of energy provided by the input power source. When the switching unit is not conducted, the energy storage element provides the driving current.

Abstract: A dimmable LED reading light unit includes comprises a dimming module and an LED module, connected in series. The dimming module has an input being connectable to a power supply supplying direct voltage and includes a potentiometer allowing section of a dimming rate and a current controller providing an operating current for the LED module. The LED module includes at least one LED and a current consumer connected in parallel and the current controller is configured to supply direct current to the LED module that substantially corresponds to the sum of the driving current necessary for driving the at least one LED to emit light with an intensity of illumination corresponding to the dimming rate of the potentiometer, and the current consumption of the current consumer.

Abstract: An electronic ballast circuit includes a power factor correction circuit, a control and amplifier circuit, a ballast controller circuit and a ballast driver circuit. The ballast driver circuit includes a resonant circuit that connects to a lamp and a strike voltage limiter circuit that regulates the behavior of the resonant circuit. An overcurrent sensor circuit may be included to indirectly the control the ballast controller circuit via the control and amplifier circuit. The strike voltage limiter circuit uses varistors to change the resonant frequency of the resonant circuit to limit the voltage to the lamp.